I'm pretty new to coding, and I'm trying to complete Codecademy's Javascript course. I've learned a little bit about HTML/CSS and I'm almost done with JavaScript. I've researched people having similar problems, but those solutions typically involve JQuery, which I haven't learned.
Here is my HTML (index.html):
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript" src="main.js"></script>
</head>
<body>
</body>
</html>
Here is the beginning of my JavaScript:
alert();
// Acquire character's name and check to make sure it's a string
var charName = prompt("NASA Receptionist: 'Welcome to Mission Control.
May I have your last name, please?'");
var nameCheck = function(charName) {
while (typeof charName === "number") {
charName = prompt("NASA Receptionist: 'Surely, your name is not
a number... Please, may I have your last name?'");
}
};
nameCheck(charName);
NOTE: index.html is in the same folder as main.js
When I open the index.html, nothing happens, not even the opening alert(). Am I missing something?
You have error in your script as you cannot make javascript statements in multiple lines without using escaping slash .
I was getting this error :
SyntaxError: unterminated string literal
var charName = prompt("NASA Receptionist: 'Welcome to Mission Control.
Here is the modified code :
alert();
// Acquire character's name and check to make sure it's a string
//The \r\n\ will format the string in prompt and make it appear in new line
var charName = prompt("NASA Receptionist: 'Welcome to Mission Control. \
\r\n\May I have your last name, please?'");
var nameCheck = function(charName) {
while (typeof charName === "number") {
charName = prompt("NASA Receptionist: 'Surely, your name is not \
\r\n\a number... Please, may I have your last name?'");
}
};
nameCheck(charName);
Check in browser source file whether main.js is loaded.
use alert("= loaded =") to check alert is called or not
If you are not even getting the syntax error, then I think you maybe referencing main.js incorrectly. Are you sure you have this in the same directory as index.html.
Also, each time I run it, the typeof method returns "string", no matter if I enter a number or not.
alert(typeof charName);
Related
I have recently started working with JavaScript and Node and I'm having trouble working with the .ejs files.
I'm trying to implement a button in my page that gets a string inserted in a textarea and runs a function to evaluate if that string is a xml code (more precisely a Vast Tag, but that's not the point.)
So, I have something like this:
<div class="clear vastClass">
<h3> Vast Tag </h3>
<div class="vastClass" hidden>
<div>
<p>Please validate your code!</p>
<input type="button" id ="buttonVast" value="Validate">
</div>
<textarea id="vastTag" name="vastTag" class="form_creatives" value="">Insert you Vast Tag</textarea>
</div>
</div>
<script>
$("#buttonVast").click(function(){
// TODO
}
</script>
So here are a few questions:
I'm trying to use the node module xml2js to see check the text and I have read something online already (I don't know if they are right). e.g.:
The browser is running the .ejs file, so if I try to require('xml2js') it won't understand
I tried to use the browserify package, but I can't seen to make it work
I can only call a file.js using if that file is in my public assets folder. (indeed any file I try to access I get an 404 Page Not Found Exception)
So, my questions is if anyone have any tips on a method that works where I can either use the node module inside my script, OR If can define a function in a file.js and then call this function into the script, OR if anyone knows how browserify works and if it can be used to fix my problem.
To check if the string in a textarea is xml you can use a regex expression. This checks to see if the input starts with
Here's a working fiddle: http://fiddle.jshell.net/mikemjharris/j1nL8rz0/
The specific code to check for xml:
function checkXML () {
var textToCheck = $('textarea').val();
if( textToCheck.match(/\<\?xml /) ) {
alert('this is xml!');
} else {
alert('not xml');
}
}
Thanks for the reply #mikemjharris, but it doesnt really solve my problem.
After a couple more days searching, I've found out how to use browserify, so I'll answer it myself.
First, I had to create a .js file, let's say, main.js, where I declared and defined all the functions I wanted to use, e.g.
Main.js:
var xml2js = require('xml2js')
validateVast = function(vast){
var parser = xml2js.Parser()
parser.parseString(vast, function(err, result){
if(result && !err){
console.log(result)
}
else{
console.log(err.toString())
}
})
}
Then, in the terminal I used the command below to add a Bundle file to my public resources folder:
browserify folder/main.js -o public/js/xml2jsBundle
Then, in my html file, I added the line
<script src="js/xml2jsBundle.js"</script>
And then was able to call my function in the body of the html like:
<body>
<script src="js/xml2jsBundle.js"</script>
<input type="button" value="Validate" class="bt_Add" onClick="validate()">
<textarea id="vastTag" name="vastTag" class="form_creatives" value=""></textarea>
<script type="text/javascript">
function validate(){
var vast = $("#vastTag").val()
validateVast(vast)
}
</script>
</body>
Well, I guess this is it.
Thanks for your help, bye
In my HTML file I have linked to the JS with:
src="myscript.js?config=true"
Can my JS directly read the value of this var like this?
alert (config);
This does not work, and the FireFox Error Console says "config is not defined". How do I read the vars passed via the src attribute in the JS file? Is it this simple?
<script>
var config=true;
</script>
<script src="myscript.js"></script>
You can't pass variables to JS the way you tried. SCRIPT tag does not create a Window object (which has a query string), and it is not server side code.
Yes, you can, but you need to know the exact script file name in the script :
var libFileName = 'myscript.js',
scripts = document.head.getElementsByTagName("script"),
i, j, src, parts, basePath, options = {};
for (i = 0; i < scripts.length; i++) {
src = scripts[i].src;
if (src.indexOf(libFileName) != -1) {
parts = src.split('?');
basePath = parts[0].replace(libFileName, '');
if (parts[1]) {
var opt = parts[1].split('&');
for (j = opt.length-1; j >= 0; --j) {
var pair = opt[j].split('=');
options[pair[0]] = pair[1];
}
}
break;
}
}
You have now an 'options' variable which has the arguments passed. I didn't test it, I changed it a little from http://code.google.com/p/canvas-text/source/browse/trunk/canvas.text.js where it works.
You might have seen this done, but really the JS file is being preprocessed server side using PHP or some other language first. The server side code will print/echo the javascript with the variables set. I've seen a scripted ad service do this before, and it made me look into seeing if it can be done with plain ol' js, but it can't.
You need to use Javascript to find the src attribute of the script and parse the variables after the '?'. Using the Prototype.js framework, it looks something like this:
var js = /myscript\.js(\?.*)?$/; // regex to match .js
var jsfile = $$('head script[src]').findAll(function(s) {
return s.src.match(js);
}).each(function(s) {
var path = s.src.replace(js, ''),
includes = s.src.match(/\?.*([a-z,]*)/);
config = (includes ? includes[1].split('=');
alert(config[1]); // should alert "true" ??
});
My Javascript/RegEx skills are rusty, but that's the general idea. Ripped straight from the scriptaculous.js file!
Your script can however locate its own script node and examine the src attribute and extract whatever information you like.
var scripts = document.getElementsByTagName ('script');
for (var s, i = scripts.length; i && (s = scripts[--i]);) {
if ((s = s.getAttribute ('src')) && (s = s.match (/^(.*)myscript.js(\?\s*(.+))?\s*/))) {
alert ("Parameter string : '" + s[3] + "'");
break;
}
}
Whether or not this SHOULD be done, is a fair question, but if you want to do it, http://feather.elektrum.org/book/src.html really shows how. Assuming your browser blocks when rendering script tags (currently true, but may not be future proof), the script in question is always the last script on the page up to that point.
Then using some framework and plugin like jQuery and http://plugins.jquery.com/project/parseQuery this becomes pretty trivial. Surprised there's not a plugin for it yet.
Somewhat related is John Resig's degrading script tags, but that runs code AFTER the external script, not as part of the initialization: http://ejohn.org/blog/degrading-script-tags/
Credits: Passing parameters to JavaScript files , Passing parameters to JavaScript files
Using global variables is not a so clean or safe solution, instead you can use the data-X attributes, it is cleaner and safer:
<script type="text/javascript" data-parameter_1="value_1" ... src="/js/myfile.js"></script>
From myfile.js you can access the data parameters, for instance with jQuery:
var parameter1 = $('script[src*="myfile.js"]').data('parameter_1');
Obviously "myfile.is" and "parameter_1" have to match in the 2 sources ;)
You can do that with a single line code:
new URL($('script').filter((a, b, c) => b.src.includes('myScript.js'))[0].src).searchParams.get("config")
It's simpler if you pass arguments without names, just like function calls.
In HTML:
<script src="abc.js" data-args="a,b"></script>
Then, in JavaScript:
const args=document.currentScript.dataset.args.split(',');
Now args contains the array ['a','b'].
I know this is really basic javascript but I'm really not so familiar with javascript.
What I'm trying here is to add prettyPhoto arguments where I want to be. First I get href attribute from link, then I convert it to string, then I take last 4 letters to check is it link to image or to some HTML page. And this code works fine but still my Firebug sends me an error:
TypeError: $hrefy is undefined
txt = $hrefy.toString();
How script can work if $hrefy is not defined and how to define it well. This error blocks only javascript code for filtering my portfolio, while other js work fine.
$(document).ready(function(){
$("a[data-rel^='prettyPhoto']").prettyPhoto();
$hrefy = $("article a").has('img').attr("href");
txt = $hrefy.toString();
var lastChar = txt.substr(txt.length - 4);
if (lastChar=='.jpg') {
$('article a').has('img').attr('data-rel', 'prettyPhoto');
}
$('a img').click(function () {
var desc = $(this).attr('title');
$('a').has('img').attr('title', desc);
});
});
After looking into the source of the page you've linked, I've noticed that there is no <article> element declared anywhere. So, your jquery selector does not return anything and attr('href') is undefined.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How can I get the content of the file specified as the 'src' of a <script> tag?
this may seem like a strange question but it's been on my mind. Say I had a HTML file that references one or many JavaScript files, these files are local but could be external. Now for some reason (my own curiosity) I wish to output the contents of one of these files like a string and write it to the console or even alert the contents. So say I have the following JS file called jsFile.js:
// JavaScript Document
var testString = "I am just an output... or am I",
testNumber = 1,
testArray = [],
testObject = {};
// random functionality, etc... etc...
if(testNumber > 100){
// do something...
}
and I want to output this like so when opening my HTML page:
however I am unsure how to do this, can I find the SCRIPT tag in the dom and use a method on it to output it's contents (see below) or do I have to read the file (somehow) then loop through each line of code collecting it in a variable, then output it by either alert or console.log
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Hello World</title>
</head>
<script type="text/javascript" src="jsFile.js"></script>
<script type="text/javascript">
// find the JS node...
window.onload = function(){
var theFile = document.getElementsByTagName("script")[0];
// none of these will work as the code within the jsFile.js is not a DOM object...
console.log(theFile.text); // returns a zero length string
console.log(theFile.innerHTML); // returns a zero length string
console.log(theFile.textContent); // returns a zero length string
}
</script>
<body>
I am just a HTML file... no more, no less...
</body>
</html>
Above is my first attempt however none of these methods will work as the contents of the script are not DOM objects. I don't need a code specific answer, just a proof of concept, idea or point in the right direction. If I'm not making sense please say so and I will reword my question.
You will need to make an AJAX request to the URL of that script and display the content where ever you want to (just grab the responseText), it is a server side resource, and the returned content will be your javascript :)
While epoch essentially has answered this already, I was triggered by this challenge, I've written a little snippet that dumps all scripting resources to the console, provided that they are upon the same domain (origin). I've tested it in Chrome.
var f = function (src) {
var origin = location.origin || (location.protocol+'//'+location.hostname);
if (src.substr(0, origin.length) != origin) {
return;
}
x = new XMLHttpRequest();
x.open("GET", src.substr(origin.length), true);
x.onreadystatechange = function () {
if (x.readyState == 4 && x.status == 200) {
console.log(x.responseText)
}
};
x.send();
};
var s = document.getElementsByTagName('script');
for (var i = 0; i < s.length; ++i) {
f(s[i].src);
}
Often I will have a JavaScript file that I want to use which requires certain variables be defined in my web page.
So the code is something like this:
<script type="text/javascript" src="file.js"></script>
<script type="text/javascript">
var obj1 = "somevalue";
</script>
But what I want to do is:
<script type="text/javascript"
src="file.js?obj1=somevalue&obj2=someothervalue"></script>
I tried different methods and the best one yet is to parse the query string like this:
var scriptSrc = document.getElementById("myscript").src.toLowerCase();
And then search for my values.
I wonder if there is another way to do this without building a function to parse my string.
Do you all know other methods?
I'd recommend not using global variables if possible. Use a namespace and OOP to pass your arguments through to an object.
This code belongs in file.js:
var MYLIBRARY = MYLIBRARY || (function(){
var _args = {}; // private
return {
init : function(Args) {
_args = Args;
// some other initialising
},
helloWorld : function() {
alert('Hello World! -' + _args[0]);
}
};
}());
And in your html file:
<script type="text/javascript" src="file.js"></script>
<script type="text/javascript">
MYLIBRARY.init(["somevalue", 1, "controlId"]);
MYLIBRARY.helloWorld();
</script>
You can pass parameters with arbitrary attributes. This works in all recent browsers.
<script type="text/javascript" data-my_var_1="some_val_1" data-my_var_2="some_val_2" src="/js/somefile.js"></script>
Inside somefile.js you can get passed variables values this way:
........
var this_js_script = $('script[src*=somefile]'); // or better regexp to get the file name..
var my_var_1 = this_js_script.attr('data-my_var_1');
if (typeof my_var_1 === "undefined" ) {
var my_var_1 = 'some_default_value';
}
alert(my_var_1); // to view the variable value
var my_var_2 = this_js_script.attr('data-my_var_2');
if (typeof my_var_2 === "undefined" ) {
var my_var_2 = 'some_default_value';
}
alert(my_var_2); // to view the variable value
...etc...
Another idea I came across was assigning an id to the <script> element and passing the arguments as data-* attributes. The resulting <script> tag would look something like this:
<script id="helper" data-name="helper" src="helper.js"></script>
The script could then use the id to programmatically locate itself and parse the arguments. Given the previous <script> tag, the name could be retrieved like this:
var name = document.getElementById("helper").getAttribute("data-name");
We get name = helper
Check out this URL. It is working perfectly for the requirement.
http://feather.elektrum.org/book/src.html
Thanks a lot to the author. For quick reference I pasted the main logic below:
var scripts = document.getElementsByTagName('script');
var myScript = scripts[ scripts.length - 1 ];
var queryString = myScript.src.replace(/^[^\?]+\??/,'');
var params = parseQuery( queryString );
function parseQuery ( query ) {
var Params = new Object ();
if ( ! query ) return Params; // return empty object
var Pairs = query.split(/[;&]/);
for ( var i = 0; i < Pairs.length; i++ ) {
var KeyVal = Pairs[i].split('=');
if ( ! KeyVal || KeyVal.length != 2 ) continue;
var key = unescape( KeyVal[0] );
var val = unescape( KeyVal[1] );
val = val.replace(/\+/g, ' ');
Params[key] = val;
}
return Params;
}
You use Global variables :-D.
Like this:
<script type="text/javascript">
var obj1 = "somevalue";
var obj2 = "someothervalue";
</script>
<script type="text/javascript" src="file.js"></script">
The JavaScript code in 'file.js' can access to obj1 and obj2 without problem.
EDIT Just want to add that if 'file.js' wants to check if obj1 and obj2 have even been declared you can use the following function.
function IsDefined($Name) {
return (window[$Name] != undefined);
}
Hope this helps.
Here is a very rushed proof of concept.
I'm sure there are at least 2 places where there can be improvements, and I'm also sure that this would not survive long in the wild. Any feedback to make it more presentable or usable is welcome.
The key is setting an id for your script element. The only catch is that this means you can only call the script once since it looks for that ID to pull the query string. This could be fixed if, instead, the script loops through all query elements to see if any of them point to it, and if so, uses the last instance of such an script element. Anyway, on with the code:
Script being called:
window.onload = function() {
//Notice that both possible parameters are pre-defined.
//Which is probably not required if using proper object notation
//in query string, or if variable-variables are possible in js.
var header;
var text;
//script gets the src attribute based on ID of page's script element:
var requestURL = document.getElementById("myScript").getAttribute("src");
//next use substring() to get querystring part of src
var queryString = requestURL.substring(requestURL.indexOf("?") + 1, requestURL.length);
//Next split the querystring into array
var params = queryString.split("&");
//Next loop through params
for(var i = 0; i < params.length; i++){
var name = params[i].substring(0,params[i].indexOf("="));
var value = params[i].substring(params[i].indexOf("=") + 1, params[i].length);
//Test if value is a number. If not, wrap value with quotes:
if(isNaN(parseInt(value))) {
params[i] = params[i].replace(value, "'" + value + "'");
}
// Finally, use eval to set values of pre-defined variables:
eval(params[i]);
}
//Output to test that it worked:
document.getElementById("docTitle").innerHTML = header;
document.getElementById("docText").innerHTML = text;
};
Script called via following page:
<script id="myScript" type="text/javascript"
src="test.js?header=Test Page&text=This Works"></script>
<h1 id="docTitle"></h1>
<p id="docText"></p>
might be very simple
for example
<script src="js/myscript.js?id=123"></script>
<script>
var queryString = $("script[src*='js/myscript.js']").attr('src').split('?')[1];
</script>
You can then convert query string into json like below
var json = $.parseJSON('{"'
+ queryString.replace(/&/g, '","').replace(/=/g, '":"')
+ '"}');
and then can use like
console.log(json.id);
This can be easily done if you are using some Javascript framework like jQuery.
Like so,
var x = $('script:first').attr('src'); //Fetch the source in the first script tag
var params = x.split('?')[1]; //Get the params
Now you can use these params by splitting as your variable parameters.
The same process can be done without any framework but will take some more lines of code.
Well, you could have the javascript file being built by any of the scripting languages, injecting your variables into the file on every request. You would have to tell your webserver to not dish out js-files statically (using mod_rewrite would suffice).
Be aware though that you lose any caching of these js-files as they are altered constantly.
Bye.
HTML:
<script src='greet.js' data-param1='hello' data-param2='world'></script>
// greet.js:
const prm1=document.currentScript.dataset.param1;
const prm2=document.currentScript.dataset.param2;
Nice question and creative answers but my suggetion is to make your methods paramterized and that should solve all your problems without any tricks.
if you have function:
function A()
{
var val = external_value_from_query_string_or_global_param;
}
you can change this to:
function B(function_param)
{
var val = function_param;
}
I think this is most natural approach, you don't need to crate extra documentation about 'file parameters' and you receive the same. This specially useful if you allow other developers to use your js file.
It's not valid html (I don't think) but it seems to work if you create a custom attribute for the script tag in your webpage:
<script id="myScript" myCustomAttribute="some value" ....>
Then access the custom attribute in the javascript:
var myVar = document.getElementById( "myScript" ).getAttribute( "myCustomAttribute" );
Not sure if this is better or worse than parsing the script source string.
Here i have found an another way of doing this same thing. In the reuired js file [cttricks.js as i have used it for testing, you can have your any .js file], we'll simply list up all script elements and get the required one as it is always going to be at last index. And then get ".attributes.src.value" from that.
Now, in any case of script call, it is
<script src="./cttricks.js?data1=Hello&data2=World"></script>
And in the cttricks.js script file,
var scripts = document.getElementsByTagName('script');
var jsFile = new URL("http://" + scripts[scripts.length-1].attributes.src.value);
/*get value from query parameters*/
console.log(jsFile.searchParams.get("data1"));
console.log(jsFile.searchParams.get("data2"));
Enjoy!!
No, you cant really do this by adding variables to the querystring portion of the JS file URL. If its writing the portion of code to parse the string that bothers you, perhaps another way would be to json encode your variables and put them in something like the rel attribute of the tag? I don't know how valid this is in terms of HTML validation, if thats something you're very worried about. Then you just need to find the rel attribute of the script and then json_decode that.
eg
<script type='text/javascript' src='file.js' rel='{"myvar":"somevalue","anothervar":"anothervalue"}'></script>
If you need a way that passes CSP check (which prohibits unsafe-inline) then you have to use nonce method to add a unique value to both the script and the CSP directive or write your values into the html and read them again.
Nonce method for express.js:
const uuidv4 = require('uuid/v4')
app.use(function (req, res, next) {
res.locals.nonce = uuidv4()
next()
})
app.use(csp({
directives: {
scriptSrc: [
"'self'",
(req, res) => `'nonce-${res.locals.nonce}'` // 'nonce-614d9122-d5b0-4760-aecf-3a5d17cf0ac9'
]
}
}))
app.use(function (req, res) {
res.end(`<script nonce="${res.locals.nonce}">alert(1 + 1);</script>`)
})
or write values to html method. in this case using Jquery:
<div id="account" data-email="{{user.email}}"></div>
...
$(document).ready(() => {
globalThis.EMAIL = $('#account').data('email');
}
Although this question has been asked a while ago, it is still relevant as of today. This is not a trivial approach using script file params, but I already had some extreme use-cases that this way was most suited.
I came across this post to find out a better solution than I wrote a while ago, with hope to find maybe a native feature or something similar.
I will share my solution, up until a better one will be implemented. This works on most modern browsers, maybe even on older ones, didn't try.
All the solutions above, are based on the fact that it has to be injected with predefined and well marked SCRIPT tag and rely completely on the HTML implementation. But, what if the script is injected dynamically, or even worse, what if you are write a library, that will be used in a variety of websites?
In these and some other cases, all the above answers are not sufficient and even becoming too complicated.
First, let's try to understand what do we need to achieve here. All we need to do is to get the URL of the script itself, from there it's a piece of cake.
There is actually a nice trick to get the script URL from the script itself. One of the functionalities of the native Error class, is the ability to provide a stack trace of the "problematic location", including the exact file trace to the last call. In order to achieve this, I will use the stack property of the Error instance, that once created, will give the full stack trace.
Here is how the magic works:
// The pattern to split each row in the stack trace string
const STACK_TRACE_SPLIT_PATTERN = /(?:Error)?\n(?:\s*at\s+)?/;
// For browsers, like Chrome, IE, Edge and more.
const STACK_TRACE_ROW_PATTERN1 = /^.+?\s\((.+?):\d+:\d+\)$/;
// For browsers, like Firefox, Safari, some variants of Chrome and maybe other browsers.
const STACK_TRACE_ROW_PATTERN2 = /^(?:.*?#)?(.*?):\d+(?::\d+)?$/;
const getFileParams = () => {
const stack = new Error().stack;
const row = stack.split(STACK_TRACE_SPLIT_PATTERN, 2)[1];
const [, url] = row.match(STACK_TRACE_ROW_PATTERN1) || row.match(STACK_TRACE_ROW_PATTERN2) || [];
if (!url) {
console.warn("Something went wrong. You should debug it and find out why.");
return;
}
try {
const urlObj = new URL(url);
return urlObj.searchParams; // This feature doesn't exists in IE, in this case you should use urlObj.search and handle the query parsing by yourself.
} catch (e) {
console.warn(`The URL '${url}' is not valid.`);
}
}
Now, in any case of script call, like in the OP case:
<script type="text/javascript" src="file.js?obj1=somevalue&obj2=someothervalue"></script>
In the file.js script, you can now do:
const params = getFileParams();
console.log(params.get('obj2'));
// Prints: someothervalue
This will also work with RequireJS and other dynamically injected file scripts.
I think it is far more better and modern solution to just use localStorage on the page where the javascript is included and then just re-use it inside the javascript itself. Set it in localStorage with:
localStorage.setItem("nameOfVariable", "some text value");
and refer to it inside javascript file like:
localStorage.getItem("nameOfVariable");
It's possible to pass parameters to js modules and read them after via import.meta.url.
For example, with the following HTML
<script type="module">
import './index.mjs?someURLInfo=5';
</script>
the following JavaScript file will log the someURLInfo parameter:
// index.mjs
new URL(import.meta.url).searchParams.get('someURLInfo'); // 5
The same applies when a file imports another:
// index.mjs
import './index2.mjs?someURLInfo=5';
// index2.mjs
new URL(import.meta.url).searchParams.get('someURLInfo'); // 5